Rotary piston compressor



Jame H, 1968 F. LUCK ROTARY PISTON COMPRESSOR 2 Sheets-Sheet 1 FiledJuly 5, 1966 4 /7/01? AKT In van for: '79s Mir) Z424 June 11, 1968 F.LUCK 3,387,771

ROTARY PISTON COMPRESSOR Filed July 5, 1966 2 Sheets-Sheet 2 ire Thepresent invention relates to a rotary piston compressor with rotarypistons eccentrically arranged one within the other and meshing witheach other. More specifically, the present invention concerns a specificembodiment of the inlet and outlet openings of rotary piston compressorsof the above mentioned type while the inner wall surface of the outerrotary piston has the contour of a trochoid, whereas the wall surface ofthe inner rotary piston has the contour of enveloping curves.

Rotary piston compressors of the above mentioned type with inlet andoutlet openings in the centers of the enveloping curves are known, whichare evenly spaced from the adjacent tooth tips.

It is an object of the present invention to provide a rotary pistoncompressor of the above mentioned type, which will have an increaseddelivery.

It is another object of this invention to provide a rotary pistoncompressor which will be characterized by a greatly increased degree ofefiiciency.

These and other objects and advantages of the invention will appear moreclearly from the following specification in connection with theaccompanying drawing, in which:

FIG. 1 diagrammaticaly illustrates a cross section through a rotarypiston compressor according to the present invention while saidcompressor occupies a position in which the piston is ahead of its deadcenter position by an angle of 30.

FIG. 2 is a section similar to that of FIG. 1 showing the piston in itsdead center position.

FIGS. 3 to illustrate cross sections through a similar compressor which,however, in conformity with the present invention, is equipped withasymmet-ricaly arranged openings. More specifically, FIG. 3 shows thepiston 60 ahead of the dead center position; FIG. 4 shows the piston 30ahead of the dead center position; FIG. 5 shows the piston in its deadcenter position.

FIGURE 6 illustrates a longitudinal section through a rotary pistoncompressor according to the present invention.

For purposes of increasing the delivery and the degree of efiiciency ofthe compressor, it is suggested in conformity with the present inventionto arrange the inlet and outlet openings asymmetrically between the tipsof the inner rotary piston. More specifically, the said openings are soarranged that they are located in that portion of the enveloping curvewhich runs ahead. At the same time, that control edge which governs thedischarge end has been displaced in the insert member in the directionof rotation of the rotary piston compressor.

According to a further development of the invention, each opening of theinner rotary piston starts approximately in the center of the envelopingcurve and extends over approximately a quarter of the enveloping curve.

Furthermore, in conformity with the present invention, that opening edgewhich runs ahead or forms the front edge when looking in the directionof rotation of piston 2 is greatly rounded toward the enveloping curveof the inner rotary piston, and the opening edge which runs behind orforms the rear edge when looking in the i ate direction of rotation ofpiston 2 is provided with a sharp edge and a sharp angle with regard tothe enveloping curve.

Referring now more specifically to the drawing, in all figures it isassumed that the outer rotary piston 1 rotates clockwise, and that theinner rotary pistons 2 and 3 are moved by the outer rotary piston 1through the intervention of coupling gears at a transmission ratio of2:3. The inner rotary piston 2 of FIGS. 1 and 2 comprises symmetric-allyarranged openings 4, whereas the openings 5 in the inner rotary piston 3of FIGS. 3 to 5 are asymmetrically arranged in the running ahead portionof the enveloping curve 6. The tips of the inner rotary piston which areusually equipped with seals 7 subdivide the cylinder chamber into threeworking chambers 8, 9 and lit in which in equal sequence there iseffected the intake, the compression and the exhaust as well as thereturn expansion.

Within the inner rotary piston 2 there is provided an insert member 11,12 which is fixedly connected to the housing lid and which comprises theinlet passage 13, 14 and the outlet passage 15, 16. The control edges ofthe passages 14 and 16 in the insert member 12 are in the same directionas the opening 5 displaced relative to the heretofore known arrangementas illustrated in FIGS. 1 and 2. The definement of the openings 4according to FIGS. 1 and 2 is effected by the sharp edge or the somewhatrounded control edges 4a and 4b, whereas with the opening 5 according toFIG. 3 the running ahead control edge 5a merges with the envelopingcurve 6 over a considerably rounded portion, while the la ging controledge 5b merges with the enveloping curve 6 along a sharp edge and asharp angle. In view of these features, advantages are obtained duringthe intake over the entire intake stroke and also during the dischargeof the working medium, especially near the dead center position. Theseadvantages will presently appear.

During the intake stroke, the working medium enters through openings 4,5 and passes into the suction chamber 8. The magnitude and the directionof the inlet velocity depend on the velocity of the working mediumitself and on the superimposed rotary speed of the inner rotary pistons2, 3 (see also FIGS. 2 and 5). According to FIG. 5, the working mediumflows to an increased extent counter to the running ahead portion of theinner wall of the outer rotary piston 1 which defines the workingchamber 8 (see FIG. 2). The flow pressure aids the rotary movement, andthe flow conditions thus approach those of pure flow machines. Thefavorable effect of the present invention is further aided by theconsiderably rounded running ahead opening edge 5a and the sharp edgedand sharp angled lagging edge 5b. The highly rounded running ahead edge5a brings about a favorable radiation spread in the direction ofrotation, whereas the sharp edged and sharp angled lagging edge 51)impedes the inflow of the taken-in working medium in the subsequentportion 81; of the working chamber 8. In this way, in this portion alower pressure is formed than in the preceding portion 8a. This pressuredrop aids in the rotary movement and in particular acts upon the innerrotary piston, while to a smaller extent it also acts upon the outerrotary piston. These conditions have been illustrated for the outerrotary piston by the higher pressure p over the lower pressure Pa"- Inconclusion it may be stated that the sharp edge 5b which impedes theflow will not cause any reduced filling of the intake chamber 8. Towardthe end of the intake stroke, i.e. ahead and after the dead centerposition, the change in the working chamber is so small that a pressureincrease including a post-charge in the entire suction chamber 8 canoccur without difliculties.

The discharge operation is effected as follows. The

Patented June 11, 1968' s,ss7,771

compressed working medium leaves the pressure chamber 19 throughopenings 4, and passes into the pressure passage 15, 16. The workingmedium has to pass the running ahead control edge 40, 5a and at the endof the discharge operation also has to pass the control edge 15a, 15a(see FIGS. 1 and 4). The cross sections which have to be passed throughby the flow and which are defined by these control edges and the innerwall of the outer rotary piston and which are indicated by a dotted line.18, 19 are, according to FIG. 4, considerably greater than those ofFIG. 1. In the drawing, the partial volume to be conveyed of the workingchamber is indicated by dash lines and according to FIG. 4 isconsiderably less than according to FIG. 1. As total result there isobtained the fact that the flow velocities in this narrow passageportion are with the arrangement according to the present inventionconsiderably lower and the supply of energy for the exhaust operation iscorrespondingly lower. During the discharge of the working medium, afurther advantageons effect is obtained by the opening edge 5b which isfurther advanced in the direction of rotation with regard to the openingedge 4b.

According to FIGS. 2 and 5, the ro ary pistons occupy their dead centerpositions. Chamber 1% occupies a minimum of space, the so-called harmfulspace. When the opening 4 is in the center of the said harmful space asillustrated in FIG. 4, communication is established be tween the twohalves of the chamber. Both halves are thus filled with a compressedworking medium. The entire quantity which is entrapped in the harmfulchamber 10 reexpands after the dead center point has been passed andreduces the intake quantity of the compressor.

According to FIG. 5, the opening edge 5b is in the center. Theenveloping curve 6 will in its dead center position with the inner Wallof the outer rotary piston 1 form a sealing gap 17 which subdivideschamber 19 into two parts and to a more or less extent prevents thecompressed working medium from passing into the left chamber portionwhich increases prior to reaching the dead center point (see FIGS. 3 to5). Therefore only or approximately only the right-hand chamber portionplus the opening space 5 forms the harmful space. As a result thereof,the rte-expanding quantity is reduced while at the same time the intakequantity of the compressor increases.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular embodiment shown in the drawing butalso comprises any modifications within the scope of the appendedclaims.

What I claim is:

1. A rotary piston compressor, which includes: an outer rotary pistonhaving its inner wall surface shaped in conformity with a trochoid, aninner rotary piston rotatably arranged in and eccentrically locatedrelative to said outer rotary piston and having its outer peripheralsurface shaped in conformity with the contour of enveloping curves so asto form a plurality of surface sections with each two adjacent surfacesections intersecting each other along a line so as to form a ridge, thesaid surface sections together with the respective adjacent inner wallsurface portions of said outer rotary piston defining portions ofworking chambers, the peripheral wall of said inner rotary piston beingprovided with a plurality of passage means respectively located betweensaid ridges and when looking in the direction of rotation of said innerrotary piston being located closer to that ridge which is in front ofthe respective passage terms than that ridge which. is behind therespective passage means, and stationary insert means provided withfluid inlet and outlet means and operable successively to communicatewith said passage means.

2. A compressor according to claim 1, in which that edge portion of saidoutlet means which defines the outet end when looking in the directionof rotation of said inner rotary piston is displaced in the direction ofrotation of the rotary compressor.

3. A compressor according to claim 1, in which each of said passagemeans of the inner rotary piston, when looking in the direction ofrotation of the latter, starts approximately in the center of therespective enveloping curve defining the contour of the outer peripheralsurface of the inner rotary piston and extends approximately over aquarter of said enveloping curve in the direction of rotation of saidinner rotary piston.

4. A compressor according to claim 1, in which that edge portion of saidpassage means which in the direction of rotation of said inner rotarypiston runs ahead of the opposite edge portion of the same passage meansis greatly rounded toward the respective adjacent outer peripheralsurface of said inner rotary piston.

5. A compressor according to claim 1, in which that edge portion of eachof said passage means which runs behind the opposite edge portion of thesame passage means when looking in the direction of rotation of theinner rotary piston is sharp-edged and sharp-angled with regard to therespective outer peripheral surface of said inner rotary piston.

References Cited UNITED STATES PATENTS FRED C. MA'lTERN, In, PrimaryExaminer.

WILBUR J. GOODLIN, Assistant Examiner.

1. A ROTARY PISTON COMPRESSOR, WHICH INCLUDES: AN OUTER ROTARY PISTONHAVING ITS INNER WALL SURFACE SHAPED IN CONFORMITY WITH A TROCHOID, ANINNER ROTARY PISTON ROTATABLY ARRANGED IN AND ECCENTRICALLY LOCATEDRELATIVE TO SAID OUTER ROTARY PISTON AND HAVING ITS OUTER PERIPHERALSURFACE SHAPED IN CONFORMITY WITH THE CONTOUR OF ENVELOPING CURVES SO ASTO FORM A PLURALITY OF SURFACE SECTIONS WITH EACH TWO ADJACENT SURFACESECTIONS INTERSECTING EACH OTHER ALONG A LINE SO AS TO FORM A RIDGE, THESAID SURFACE SECTIONS TOGETHER WITH THE RESPECTIVE ADJACENT INNER WALLSURFACE PORTIONS OF SAID OUTER ROTARY PISTON DEFINING PORTIONS OFWORKING CHAMBERS, THE PERIPHERAL WALL OF SAID INNER ROTARY PISTON BEINGPROVIDED WITH A PLURALITY OF PASSAGE MEANS RESPECTIVELY LOCATED BETWEENSAID RIDGES AND WHEN LOOKING IN THE DIRECTION OF ROTATION OF SAID INNERROTARY PISTON BEING LOCATED CLOSER TO THAT RIDGE WHICH IS IN FRONT OFTHE RESPECTIVE PASSAGE MEANS THAN THAT RIDGE WHICH IS BEHIND THERESPECTIVE PASSAGE MEANS, AND STATIONARY INSERT MEANS PROVIDED WITHFLUID INLET AND OUTLET MEANS AND OPERABLE SUCCESSIVELY TO COMMUNICATEWITH SAID PASSAGE MEANS.